1. Field of the Invention
This invention relates to a heat radiation control device for controlling the temperature of an apparatus which is used in a vacuum and produces heat during operation.
2. Description of the Prior Art
Since discharge of heat in a vacuum, especially in space, is made only by radiation, it is hard to control the quantity of radiant heat to maintain apparatus at a given temperature. In a conventional method of heat radiation control, for example, an apparatus is provided with a radiating surface to radiate the maximum quantity of heat produced by the apparatus, and, if the quantity of heat produced by the apparatus is not large enough, the temperature of the apparatus is controlled by adjusting the quantity of produced heat with use of an auxiliary heat source, such as an electric heater, to match it to the quantity of radiant heat.
In space, however, the available electric power is often limited, so that there is conventionally used a thermal louver including no electric heater, as shown in FIG. 1.
In FIG. 1, numeral 1 designates a base plate the under surface of which is fitted with main and auxiliary bellows 2 and 3 with a space between them. The respective lower ends of these bellows 2 and 3 are pivotally mounted on a horizontal arm portion of an L-shaped swing lever 4 with its bent portion pivotally supported. Numeral 5 designates a horizontal coupling rod on which a plurality of louver members 6 are pivotally mounted at regular intervals. When one of these louver members 6, which is pivotally mounted on the bottom end of a vertical arm of the swing lever 4, is rocked, the remaining louver members 6 are also rocked through the same angle with the aid of the coupling rod 5. Numeral 7 designates a tension spring for urging the swing lever 4 to rock clockwise.
In the thermal louver of the aforementioned construction, a working fluid in the main bellows 2 is expanded by heat which is produced by an apparatus (not shown) mounted on the base plate 1 and is transferred through the base plate 1. Accordingly, the main bellows 2 is extended to rock the swing lever 4 counterclockwise. As a result, all the louver members 6 are rocked counterclockwise through an angle corresponding to the degree of extension of the main bellows 2, that is, the louver is opened to start heat radiation from the base plate 1. Thus, the opening of the louver members 6 is adjusted for the control of the temperature of the apparatus.
The thermal louver of this type, however, constitutes quite a complicated radiant heat transfer system, and it has been difficult to work out a thermal design in consideration of external incident light. To avoid such difficulty, the louver is covered with a flat radiating surface to simplify the influence of the external incident light. In this case, however, the radiating surface would retard direct heat radiation from the base plate to deteriorate the efficiency of heat radiation.